Various tubular membrane separation apparatus are already known. Many of these apparatuses are not provided with a liquid collector tube for the separation element, or include a plurality of separation elements which are housed in a single liquid collector tube. There are a few separation apparatuses in which each liquid collector tube houses a single separation element and the components are separable for cleaning and can be reassembled. Published Examined Japanese patent application Sho No. 52-37994 discloses a separation apparatus comprising a tubular support member having a large number of pores in its peripheral wall and accommodating a tubular semipermeable membrane in its interior. This apparatus includes a gasket of special shape and involves the problem of necessitating a special tool and skill for the removal and installation of the tubular semipermeable membrane.
Other separation apparatuses also have problems. The semipermeable membrane is inconvenient or costly to replace since the separation element is joined to an expensive porous pressure-resistant tube. When not separable into individual parts, the apparatus can not be cleaned and is liable to have sanitation troubles. Gaskets of special shape, if used for securing the liquid collector tube, support member and separation element, render the apparatus costly.